# std::atomic_ref<T>::operator++,++(int),--,--(int)

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< cpp‎ | atomic‎ | atomic ref

Provided only when `T` is an integral type other than cv bool or a pointer-to-object type |  |
value_type operator++() const noexcept; | (1) | (since C++20)
value_type operator++( int ) const noexcept; | (2) | (since C++20)
value_type operator--() const noexcept; | (3) | (since C++20)
value_type operator--( int ) const noexcept; | (4) | (since C++20)

Atomically increments or decrements the current value of the referenced object. These operations are read-modify-write operations.

1) Performs atomic pre-increment. Equivalent to return fetch_add(1) + 1;.
2) Performs atomic post-increment. Equivalent to return fetch_add(1);.
3) Performs atomic pre-decrement. Equivalent to return fetch_sub(1) - 1;
4) Performs atomic post-decrement. Equivalent to return fetch_sub(1);.

- For signed integral types, arithmetic is defined to use two’s complement representation. There are no undefined results.
- For pointer-to-object types, the result may be an undefined address, but the operations otherwise have no undefined behavior. The program is ill-formed if std::remove_pointer_t<T> is not a complete object type.

These overloads participate in overload resolution only if std::is_const_v<T> is false.

### Return value

1,3) The value of the referenced object after the modification.
2,4) The value of the referenced object before the modification.

### Notes

Unlike most pre-increment and pre-decrement operators, the pre-increment and pre-decrement operators for `atomic_ref` do not return a reference to the modified object. They return a copy of the stored value instead.

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 3508 (P3323R1) | C++20 | increment and decrement operators were meaningless for const T | constrained to accept only non-const `T`

### See also

fetch_add | atomically adds the argument to the value stored in the referenced object and obtains the value held previously (public member function)
fetch_sub | atomically subtracts the argument from the value stored in the referenced object and obtains the value held previously (public member function)
operator+=operator-= | atomically adds to or subtracts from the referenced value (public member function)
operator&=operator|=operator^= | atomically performs bitwise AND, OR, XOR with the referenced value (public member function)

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